Method of making titanium alloys



United States METHODF .MAKING'TITANIUM ALLOYS Douglas S. Chisholm andDon F. Hall,l\/Iidland, Mich, assigpors to The Dow Chemical Company,Midland, -Mich, a corporation of Delaware NojDrawing. ApplicationFebruary 11, 1953, :Serial No. 336,432

'2 Claims. (Cl. 75*84.5)

appended :claims means any solid element or group of .solid. elementscapable of forming. analloy with titanium,

e. :g. Ag, -Al, Au, B, Be, Bi, C, Cb,'Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf,In, Ir, Mn, Mo, .Ni, Os, Pb, Pd, Pt, Rh Sb Si, Sn, Ta, Tl, Th, U, V, W,Zr.

"ln'ourcopending application'Serial No. 315,604, filed October 20, 1952,we have disclosed and claimed a method of reducing titaniumtetrachloride vapor with magnesium to form a sponge of titanium.According to the method so-disclosed, the magnesium is used in the formof particles which are deposited as a pile upon a supporting surface,such as a steel plate, the temperature of which is subject to control.The titanium tetrachloride vapor to be reduced forms the atmospherearound the particles which are permitted to burn in the titaniumtetrachloride vapor at only a smoldering pace that is without producinga noticeable flame by abstracting a suflicient amount of the heat of thereducing reaction through the supporting surface to keep the burning ofthe particles at a smoldering pace. As the magnesium particles thussmolder titanium sponge forms along with molten magnesium chloride as aby-product which partly drains out of the sponge. After the smolderingceases, the resulting titanium sponge, which still contains somemagnesium chloride, is removed from the supporting surface as byscraping. The magnesium chloride in the sponge is removed in anysuitable manner as by sublimation, leaving chloride-free titanium spongeas the end product.

We have now discovered that by including a solid alloying element inparticulated form with the particulated magnesium, which is subjected toa controlled smoldering in titanium tetrachloride vapor as in theforegoing method, an unmelted solid titanium sponge is obtained in whichthe alloying element is uniformly distributed throughout the sponge.Subsequent melting of the sponge yields a uniformly alloyed titanium.The invention then consists of the improved alloying method herein fullydescribed and particularly pointed out in the claims.

In carrying out the invention, the particle size of the element to bealloyed with the titanium does not appear to be sharply critical,although better alloying results are bad with small particles, such asthose passing through a No. 50 standard sieve with 90 percent retentionon a No. 325 sieve. Particles smaller than those passing through a No.325 sieve are not desirable. The particle size of the magnesium used ispreferably made Patented Oct. 9, 1956 about the same as that of thealloying element. 'TTlie particulated alloying element and theparticulated magnesium are mixed together so as to form a uniform'mixture of the alloying element and the magnesium. The relative amountsof the alloying element and magnesium used depends upon the proportionof alloying element it is desired to produce in the titanium alloy to.be made. The proportions may be determined by due-consideration of thestoichiometrical relations involved in'the reaction which ensues whenthe mixture-of magnesium and alloying element is subjected to smolderingin an atmosphere of titanium tetrachloride in accordance with theinvention. In the smoldering reaction, the magnesium reacts with thetitanium tetrachloride without substantial attack on the aloying elementaccording to the following equation:

'2 .-Mg+TiCl4=Ti+2 *Mg'Clz From this equation, it is manifest that oncompletion of the reaction 48.64 pounds of magnesium theoretically yield47.9 pounds of titanium, or to produce 99. pounds of titaniumtheoretically requires Hence, to produce 100 pounds of titanium alloycontaining 1 percent of alloying element requires 101.6 pounds ofmagnesium mixed with lpound of alloying element.

In other word, the mixture of magnesium and alloying element to producea titanium alloy containing 1 percent alloying element requires amagnesium-alloying element mixture containing of alloying element in themixture of particulated alloying element and particulated magnesium.Other proportions may be calculated in similar manner.

The mixture of particulated magnesium and particulated alloying element,in the proportions necessary for the production of the desired titaniumalloy composition, is deposited upon a temperature-controlled supportingsurface in an atmosphere of titanium tetrachloride vapor in a reactionzone where the reduction of the vapor is to take place. The supportingsurface is suitably heated to a temperature sufiicient to initiatesmoldering of the magnesium in the mixture, a temperature of about 500to 950 C. being suflicient. After smoldering begins, heat is removedfrom the smoldering pile, as by cooling the supporting surface, at arate sufiicient to prevent the pile from bursting into flame whilemaintaining combustion at a smoldering pace until the magnesium isconsumed. As the magnesium smolders, metallic titanium forms in situ asa solid sponge with the particles of alloying element, originally mixedwith the particulated magnesium, uniformly distributed in the spongetogether with magnesium chloride as a by-product. It is preferable tomaintain the supporting surface at least 'hot enough to melt theby-product magnesium chloride (M. P. 708 C.) so that much of it willdrain off the sponge while forming. After the sponge containing thealloying metal has formed, it may be dislodged from the supportingsurface by means of a cooled scraper and removed from the titaniumtetrachloride vapor reaction zone. The residual magnesium chlorideremaining in the sponge after draining and the removal from the titaniumtetrachloride vapor reaction zone may be removed in any suitable manner.A preferred method of removing the residual magnesium chloride is tosubject the crude sponge to sublimation by heating it in an inertatmosphere to a temperature sufiicient to vaporize off the magnesiumchloride. The resulting chloride-free titanium 101.6 pounds of magnesium100=0.985 percent sponge containing the alloying element may be workedinto massive uniformly alloyed titanium metal by melting, as by means ofan electric arc in an inert atmosphere, and solidifying the meltedsponge.

The following example is illustrative of the practice of the invention:

Example 150 pounds of atomized magnesium and 4.5 pounds of atomizedaluminum, passing through a No. 20 standard sieve but not through a No.200 standard sieve, and 7.5 pounds of electrolytic chromium powder,passing through a No. 200 standard sieve but not through a No. 325standard sieve, were mixed together to form 162 pounds of a uniformmixture of the three particulated metals. The mixture was fed onto amoving hearth maintained at a temperature of 750 C., the rate of feedand travel of the hearth resulting in the formation of a train of themetal particles on the hearth about $42 inch deep, 1 /2 inches wide atthe rate of 1 lineal foot per minute. An atmosphere of titaniumtetrachloride vapor was maintained around the train at a pressure ofabout 4 inches of water above atmosphen'c pressure. The train smolderedon the hearth as the train formed and reached reaction temperature andincreased in bulk as the magnesisum in it was consumed forming titaniumsponge at the rate of about 1 lineal foot of sponge per minute, andmolten magnesium chloride. The molten magnesium chloride partly drainedout of the sponge as it formed. After the magnesium was consumed, asindicated by the cessation of smoldering, the resulting sponge wasscraped ofi the hearth, removed from the titanium tetrachloride vapor,and collected.

During the collection of the sponge, 17 samples were taken atapproximately equal intervals of time and analyzed for Al and Cr. Theaverage of the analysis showed an Al content of 2.9 percent and a Crcontent of 5.2 percent and the maximum deviation of the individualanalysis from the average did not exceed 10.14 per cent. Six samples ofthe sponge were are melted together in a water cooled copper mold in aninert gas atmosphere forming a titanium alloy ingot of uniformcomposition having a density of 0.163 pounds per cubic inch.

We claim:

1. The method of making an alloy of titanium and a solid elementalloyable therewith which comprises forming a mixture of magnesium inparticulate form with the alloying element in the particulate form,supporting the mixture on a surface in an atmosphere of titaniumtetrachloride vapor, and maintaining the surface of support at atemperature permitting the magnesium to burn only at a smoldering pacewhereby titanium sponge is formed having uniformly dispersedtherethrough the alloying element, and removing the so-obtained titaniumsponge from the surface of support and the titanium tetrachlorideatmosphere.

2. The method according to claim 1 followed by melting the titaniumsponge and solidifying the melted sponge.

References Cited in the file of this patent UNITED STATES PATENTS1,373,038 Weber Mar. 29, 1921 2,205,854 Kroll June 25, 1940 2,616,800Wartman Nov. 4, 1952 FOREIGN PATENTS 386,621 Great Britain Apr. 13, 1931

1. THE METHOD OF MAKING AN ALLOY OF TITANIUM AND A SOLID ELEMENTALLOYABLE THEREWITH WHICH COMPRISES FORMING A MIXTURE OF MAGNESIUM INPARTICULATE FORM WITH THE ALLOYING ELEMENT OF MAGNESIUM IN PARTICULATEFORM WITH THE MIXTURE ON A SURFACE IN AN ATMOSPHERE OF TITANIUMTETRACHLORIDE VAPOR, AND MAINTAINING THE SURFACE OF SUPPORT AT ATEMPERATURE PERMITTING THE MAGNESIUM TO BURN ONLY AT A SMOLDERING PACEWHEREBY TITANIUM SPONGE IS FORMED HAVING UNIFORMLY DISPERSEDTHERETHROUGH THE ALLOYING ELEMENT, AND REMOVING THE SO-OBTAINED TITANIUMSPONGE FROM THE SURFACE OF SUPPORT AND THE TITANIUM TETRACHLORIDEATMOSPHERE.